import java.util.LinkedList;
import java.util.Queue;
public class Main {
    public static void main(String[] args) {
        Queue<Integer> q = new LinkedList<>();
        q.offer(1);
        q.offer(2);
        q.offer(3);
        q.offer(4);// 从队尾入队
        System.out.println(q.size());
        System.out.println(q.peek()); // 获取队头元素
        q.poll();
        System.out.println(q.poll()); // 从队头出队列，并将删除的元素返回
        if (q.isEmpty()) {
            System.out.println("队列空");
        } else {
            System.out.println(q.size());
        }
    }
}
